Hearing Preservation Techniques for Vestibular Schwannoma Resection

William Couldwell

September 19, 2022


- Colleagues and friends, thank you for joining us for another session of the virtual operating room. My name is Aaron Cohen. We have another great session by Dr. Bill Caldwell, Chair at University of Utah. Bill has been of a tremendous impact on The Neurosurgical Atlas. We started working together on the Atlas since 2011, so it's been over a decade of working with Bill. It's been a tremendous experience. From the early years of the Atlas, he was our incredible supporter and contributor. He has, in fact, contributed more to the Virtual OR Grand Rounds than any other speaker. He's a master surgeon. Today, he's going to talk to us about hearing preservation strategies during resection of acoustic neuromas and more specifically about middle fossa approach. Bill, I'm truly indebted to you as a mentor and incredible surgeon. You have not only be a great colleague, a great friend, great human being. And very much looking to learning more from you today. Thank you.

- Well, thank you, Aaron, so much for that kind introduction. It's really an honor to be involved with the Atlas. It's such a great contribution to worldwide education and I'd like to talk today about hearing preservation techniques with vestibular schwannoma resection. And when we think of acoustic tumors, so this is where I'm from, we think about often these large tumors. This is a patient with neurofibromatosis type 2 with bilateral acoustic neuroma. And the tumors start in this Obersteiner-Redlich zone, the junction between peripheral and central myelin on the eighth nerve. And this can be variable, but most often it's within the canal, the internal laboratory canal, and thus can interfere with hearing very early on in the course of the disease. The classic appearance is sensorineural hearing loss usually in the higher frequencies initially and then can result in a deafness if the tumor continues to grow and progress. This is the Koos grading system that we prefer to use. I'll be talking more about the small tumors today. The stage I tumors are confined to the internal auditory canal. The stage II extend into the cistern, but don't touch the brains stem. The stage III tumors touch the brain stem. And the stage IV tumors have compression on the brains stem and significant compression on the cerebellum as depicted here. Here are just analogous images from radiology images. Here's a Koos 1, Koos 2, Koos 3, and Koos 4. And the problem with the grading system is it's not perfect. We have some tumors that defy classification by this grading system. What would you call this? They don't have a five. This is a close to 10-centimeter tumor. It's everywhere in the canal all through the temporal bone. And if we have time at the end, I'll show you how we resected this. Or tumors can also grow laterally in through the cochlea and extend even through the fallopian canal. Now obviously, you have to differentiate this from a facial neuroma, but this is often done at the time of surgery when you look at the tumor itself. This is an important one I just wanted to bring out. I'm not sure whether it can see on this image, but we can get fooled by the current protocols that they're using to do MRIs for small tumors, and I'll tell you how that can happen. If there is not a regular T1+ contrast or T1 without contrast, this is actually a lipoma. We published this case because you can get fooled if you have intrinsically high signal intensity lesion like a lipoma that's high signal intensity on images, regular MR images. And if they only give you fat-suppressed images, you can miss the lipoma. And then when you do the T1+ contrast, you see the high signal intensity, but it's actually not enhancing. So this is a pitfall and you need to really be careful when you look at the images to make sure you have a T1 without, with no fat suppression because it'll be high in signal intensity. It's a rare lesion, but it's a pitfall and I just warn you. So you want to have the complete spectrum of images available for your review. So let's go to video, Luke. This is just a very large tumor, but I'll just show you the sort of technique that I use. This is a is an elderly woman with a large tumor with hydrocephalus Koos 4 and I'll show you the the opening. We do it in a lateral position for these retrosigmoid approaches, and I'll use a retrosigmoid in this case. I like a retrosigmoid for very large tumors because it gives me a better perspective of the posterior fossa, although we'll do, as you'll see, translabyrinthine and transcochlear for large tumors as well. So retrosigmoid approach, standard neurosurgical approach, expose the sagittal or the transverse sinus and the sigmoid sinus. I'm coming on the tumor and I'm identifying the IAC. And we'll go ahead and open up the IAC, peel back the dura overline, the posterior lip of the IAC, and then go ahead and drill that. And we can do this at the beginning or the end, it doesn't really matter. I'll often decompress the tumor to allow it easier to drill the IAC, and then expose the canal component here. Use one of my hook dissectors there to really sound the center of the IAC. So you can open up the dura over this area and then you're on the facial nerve and you can dissect the tumor from the facial nerve in this location. Now we'll go ahead and debulk this tumor. Now when I'm debulking, it's important to really open it up. Don't create a small hole. Open it up widely and then use your ultrasonic aspirator to take it down like an ashtray. And that then if you maintain your capsule, I'll use this soft cottonoid dissection technique to peel the arachnoid down with a soft cottonoids and then identify the region of the brainstem. There's the seventh nerve that we've located at the root exit zone of the brainstem. We'll stimulate that. So you'll find eight first and then seven we'll, we don't cut eight until we've identified and can stimulate seven, and then dissect it from the IAC. And then most of the dissection is in this direction from medial to lateral. So it's a game of reducing the internal component of the tumor, taking the capsule of the tumor down appropriately, finding the facial nerve both distally and proximally, and then dissecting the facial nerve off. I use these otology hooks to help with the dissection. And then once we have the facial nerve completely dissected off, we'll remove the tumor. We'll close up the tumor. Use a fascial graft or an AlloDerm. And then depending on the size of the opening, we'll use Medpor cranioplasty, or a burr hole cover. So let's go to slides now, Luke. So that's the a standard way we do a large tumor. I don't set the patient up because of the medical legal issues with the anesthetic position in this country. And we do this operation so frequently that we're very comfortable with doing it in lateral position. Let's talk about hearing preservation, which I think should be more top of mind than it is. When I travel around the world, I see all these smaller tumors still being sent for radiosurgery. And I'm going to make a case to you that we should consider surgery for these smaller tumors. And I'm gonna back it up by the numbers that we're just publishing now. Let's take a look at this tumor. Let's go to video. This is a smaller Koos 3 tumor in a woman with a what we call a medial acoustic. Now, she had a cardiac pacemaker, so she doesn't have an MRI but you can see the tumor there. Now, I call these medial acoustics because they really start outside the canal and hearing is often preserved. And so, we're gonna do a hearing preservation operation here We'll preserved hearing, so the same technique. Debulk the tumor really quite radically and then dissect the capsule off the nerve complex. This is the seventh and eighth nerve complex and you'll see I'm using these soft cottonoids to help with the dissection. And if the tumor's dissectable, it comes off easily this way. And I'm using what we call Wonder Hook in my right hand. We've just reconfigured these instruments for neurosurgical applications. And then, we'll continue reduce the capsule as necessary when it becomes redundant. And then again, lift it up. If the nerve is really stuck to the tumor, we'll do a lateral dissection and dissect the tumor off laterally. And you'll see this right here and do a sharp dissection there, and then we'll remove the tumor. We'll go ahead and stimulate the seventh nerve and we're using ABRS all the time during surgery. And we'll just make sure the internal auditory canal is completely clear of tumor. We'll wax where we've drilled the internal auditory canal and then placed fat in the drilled internal auditory canal. And I hold this in place with fiber and glue. This is a trick that Al wrote and taught me and I think is a good one because you can miss air cells that you drill into that you can't see. And then, we'll go ahead and close with a large burr hole cover in this case. Let's go back to the slides, Luke. Okay, so when we're drilling the posterior canal, you wanna take a look at the CT and you'll see the posterior semicircular canal here and we're going to drill this aspect of the bone right there. And so, you need to really measure and see how much distance you have before you violate the semicircular canal here. And so you need to look, and I'll look at the MRIs and look at the CT, to see if I'm able to get to the end of the canal using a retrosigmoid approach like this and whether I'm going to be able to get to the end of the tumor most importantly. Because I don't like to dissect blindly with a hook, I like to really dissect it open and really dissect it free of the nerves, so I make sure that we get the tumor completely out of there. So this is the hearing scale that we use. Basically, class A and B hearing is the 50-50 rule that we're all taught as residents. And this is an important aspect of considering hearing preservation operations because it's one of the most important factors in determining how well you're going to do. Because the better the patient's hearing, the better chance you have preserving the hearing. Now when you think about hearing preservation operations, there's two possible outcomes. So if the patient, first of all, I don't do hearing preservation operations or any operations on acoustics that are completely incidental. We usually wait till the tumors demonstrated growth or the patient starts to lose hearing. And in either one of those situations, if you look at the natural course of hearing loss with observation, the patients lose hearing over five to 10 years. And I'll show you the curves for that. So the case that we make for trying to remove the tumor is that if you can remove it at the early stages when they still have good hearing, then you preserve quality of life better than the natural history. If you do not preserve hearing with the operation, you've actually given them a hit in their quality of life initially and you haven't given them any help but you have taken the tumor up. So we published this paper several years ago with the first 75 patients that we looked at. And this middle fossa approach was devised by Will House in the 1960s. He was a brilliant man. He died just a few years ago in Oregon. And when I was young, we used to work with the House Group when I was in Los Angeles. So I know the House Group quite well. And if you think about the middle fossa approach, what you're going to do is you're gonna identify a few key structures. So you'll see us do this in the video. Extradural middle fossa approach, we look for the RQ at the eminence which is a rough estimation of the superior semicircular canal. The GSPN, which shows you where the carotid is. and find the GSPN and then try to stimulate the GS or the geniculate nucleus and get facial nerve stimulation in this location. And then you make an a line and an angle between the arcuate eminence and the GSPN. And if you split that line, dissect that line, that's a rough estimation where the internal auditory canal is. Now the cochlea is anterior in this corner, so we'll leave roughly a three millimeter cuff in here so we don't violate the cochlea. So, this is the name of the game. You find the posterior aspect of the petrous ridge. You march down extradurally and you identify this angle, bisect the angle, and start drilling here and identify the canal. This is just showing this schematically. So what you'll find is when you identify the canal, you'll open up the dura. And the liability with this approach is the facial nerve. This is left side of patient. The facial nerve lies on top of the tumor and as you know, it's anterior in the canal. And what we'll do is we'll try to mobilize the facial nerve off the top of the tumor and then debulk the center of the tumor and then lift the tumor off of the nerves below. And the cochlear nerve is below the facial nerve here from this approach. It's inferior. You're not going to see it early on. You'll see the vestibular nerve and you'll see the facial nerve, but you won't see the cochlear nerve till the tumor's almost completely removed. And the idea here is is that you're taking a canal where the facial nerves lying on top of the tumor here, superior vestibular, inferior vestibular, or cochlear nerve, and you're gonna open this canal. And you're gonna open it past 180 degrees so that you can dissect the tumor off the nerves and lift the tumor off the cochlear nerve without compressing it while you're trying to remove it. So that's the name of the game and I cannot emphasize that enough. You need to open the canal properly and you need to open it without violating the cochlea or the labyrinth. So again, opening the canal, here's the middle fossa exposure and I'll show this to you on a video. Let's run the video. So this is a 55 year old man with hearing loss. He's got a Koos 1 tumor on the left side and you can see it occupying the canal. And this goes right to the end of the canal almost. So it would be difficult to remove by a retrosigmoid approach without under direct visualization. So we'll use this sort of semi-curved incision, open up the temporalis muscle, get right down and center this over the root of the zygoma. Okay, right here. Put two burr holes, one here and one superiorly, and lift a four by four centimeter bone flap centered on the root of the zygoma. Okay, so we're coming in extradural now, middle fossa, and we're identifying the posterior aspect of the petrous bone. And you can see what's happening. This is left side, remember. So what I'm doing is I'm identifying the posterior aspect of the petrous bone. And here's this line where you bisect the arcuate eminence and the GSPN. We call it Brackmann's line after Derald Brackmann. And so we're opening up the canal and identify, you'll see when we're opening the dura here, we'll flip the dura forward. And now, you'll see the facial nerve line right there. Right here is the facial nerve. Okay, so now what I'm doing here is I'm dissecting the facial nerve off the tumor and we'll go ahead and debulk the tumor. And I'm lifting it out. You see this, I've moved the facial nerve away, which is lying right here. And we're now rotating the tumor up out of the canal, taking care to not injure the facial nerve right here. So you have to find that plane, debulk the tumor, and lift it out autraumatically so you're not pushing on anything and constricting it. So you need to have the canal wide open so you can just lift it out of there. Go ahead and wax the air cells from the opening, we'll put a piece of fat in the IAC and then fibrin glue. And then, we'll go ahead and replace the bone flap and usually a little Medpor cranioplasty inferiorly where we've drilled out the middle fossa floor flap. And then, go ahead and do a routine closure.

- Bill, I wanted to ask you a question here. I routinely use lumpectomy for these just because it relaxes the temporal lobe and it helps. Is that been your practice or not?

- I haven't. We haven't. You know, we've had such great luck with TIVA anesthesia, that's total intravenous anesthesia. We've written a review on that and our anesthesiologists are real masters with that. And the one thing that I would say is I'm always a little concerned about too much retraction on the temporal lobe when you take the CSF out. Because I do think the CSF is a little bit of a buffer if you leave the dura closed. Now ultimately, you're opening the dura and you're getting a CSF leak when you're taking the tumor out and I understand that. But during the initial part of the retraction, I think it's a bit of a buffer. And we hadn't any problems at all. And you'll see this series with injury to the temporal lobe with this technique. So, let's talk about hearing preservation operations. So, you can use a middle fossa or retrosigmoid and I've shown you both. Now, the advantages of the middle fossa over the retrosigmoid include better hearing preservation rates and better exposure to the lateral IAC. And you complete the bone drilling prior to dural opening. The limitations, however, and I showed you this on the last video, you have limited exposure to the posterior fossa. So if the tumor's big in the posterior fossa, it's very difficult to remove 'cause you can't see the nerves. They're going beneath you. And higher incidence of facial paresis because you have to remove the facial nerve off the top of the tumor. And so you manipulate the facial nerve more for a small tumor with a middle fossa approach, but it's usually a minor facial weakness. And so, it's insignificant in my mind in the long-term and the risk of seizure is impossible with dominant temporal lobe, although we haven't had problems with that, with careful anesthesia technique. Now as I said, the most important factor when you're considering is you wanna do this operation on a patient with fairly good hearing to start with. We don't preserve bad hearing in general. Now when we published this paper a few years ago, we had about 76% hearing preservation using carefully selected patients with a middle fossa approach. And I'm going to update this, but basically the tumor size and the hearing class were the most significant important features in how to preserve hearing. But there are many cases that I do where I just don't know how I lost the hearing. So everything went perfect and usually I can predict facial nerve paresis very well 'cause we can stimulate it and we use the press electrode and the NIM monitor and we stimulate it during surgery. With the hearing, it's usually a binary phenomenon. You've got it fine. You've got wave five and then you're going along your in, you're dissecting, and all of a sudden you lose it. And so, it's very frustrating. And so, I charged two of my excellent fellows from a year ago to go through our series completely, you know, boil the ocean and find out exactly if there are any factors that could really predict hearing loss. Because I was really, I sort of, I reached an asymptote where we've reached about 80% hearing preservation in the most recent series and I can't seem to improve it. And I wonder if there's other factors besides the technical factors and I'm gonna talk about those now for the rest of the talk. So we looked at 131 cases where we attempted hearing preservation. And we tried to correlate the features during surgery. And the radiographic features and the presentation of the patients with the hearing outcomes. And I'm gonna show you the features that we looked at radiographically with this overlap of the cochlea, with the fundus of the canal. So here's the cochlea, this little mushroom thing anteriorly at the end of the canal. Modiolus is there. And in some cases, the relationship of the canal to the cochlea is different insofar the cochlea may be at the apex here or it may be lying alongside. And you can imagine if you're drilling up the end of the canal and there's a lot of overlap with the cochlea lying alongside the canal, that you may enter it with the drilling. And we think this is a feature that is important for people to know. The other thing is this extension to cochlea. So if we see this, if it's going through the modiolus, it's going into the cochlea and they can do that, we don't bother with the hearing preservation operation because it's going to be futile. And then obviously the fundal cap, this has been published before, the distance between the end of the tumor and the end of the canal. So this is the most extreme situation. This is a very good situation. So this is this overlap business I was talking about and this is a nuanced one, but here you have a large overlap. So if you imagine if you're drilling the canal, it would be easy to get into the cochlea on this particular case. And in this one here, a little less so because the canal is this and the cochlea is sort of a cap on the end of it. Enhancing tumor, obviously this is what it looks like. But we also looked at DWI signal in the IAC, which is interesting and there's not much literature on this. We've found that there's a high instance of hearing loss when we had high DWI signal. And I'll show you the data. So this is the baseline data for our patients, the Koos grade. Most of these were Koos 1 and 2 as you can imagine. And this is obviously the patients that we're trying to preserve hearing in these patients with serviceable hearing with Koos grade 1 and 2 tumors. This is the AAO hearing class prior to surgery. And then this is the hearing preservation. And this is a complicated table, I'm not gonna walk you through it because of time, but I'll give you the punchline. This is pure tone audiometer and word recognition score. And we looked at both of these features and we found which ones had good hearing that we preserved and which ones we didn't. And we found the most important factors for preserving hearing were the preoperative hearing grade, as I've mentioned, which was no surprise to us, which was identified previously in the literature. However, patients with intra-operative hypotension and the use of intra-operative vassopressors were also significantly associated with hearing loss. And also, the overlap in this fundus to cochlea. So the relationship of the cochlea to the fundus of the canal, making it more likely to be violated with the drilling and the distance and the to the cochlea. And also an important one is a duration of anesthesia. And I think this is probably, it's a chicken and egg phenomenon in my mind. That the more difficult dissections take us longer and take me longer to remove the tumor. If they're easy and the tumor comes out easily, it's a short operation and it's a very effective operation. So we also noted that you can have this high DWI signal in the cochlea. And we found this was really a high likelihood of causing hearing loss as well as overlap of fundus and tumor touching the modiolus. Most of these people lose hearing. So here's the hearing outcomes. Again, these were three significant factors in unable to be a preserved hearing in these patients. So let's talk about your options for a small tumor 'cause this is the the take home message that I have. So Jean Regis published this paper stating that radiosurgery was a superior option than a wait-and-see approach. And I think it is. So I think this is a very telling graph. If you see a wait-and-see management, most people, as I said, will lose hearing over five to 10 years. That's a natural history. So if you do lose, start to lose hearing with a small tumor, this is what your natural history would be. And you can lessen this curve by treating it with radiation therapy, gamma knife, fractionated, whatever you like to do. You can lessen the slope of the curve. But if you follow these patients over time, you can see that the curve is still going down. And if you wait long enough, most of the patients after radiation will lose hearing as well. So the point being is that if you can preserve the hearing with the hearing preservation operation, it's more durable. And about 75% of people over five, and I'll show you some of the literature on this, over five to 10 years will retain their hearing after a hearing preservation operation. So it's more effectively preserved if you can remove the tumor early and when the hearing is still good. So let's talk about neurofibromatosis type II which is a real nemesis. This was a systematic review of close to a thousand patients and I think this is a good message. Is it the mean five year local control rate with for SRS was 75% and for surgery was 8.1. So radiosurgery preserves the control better, but the hearing preservations were a little bit better and facial nerve preservations were higher after radiation. So the hearing and facial nerve preservations were 40% and 90% percent respectively for SRS and 52%. So hearing was a little bit better preserved with surgery and I presume this is surgeons using fairly conservative approach so that they don't hit, they hurt the hearing in these patients. And they do an operation to do both the tumor to preserve the hearing. So these are complicated tumors to manage, that's a whole nother talk. And you need to optimize the control. So we'll really plan when we do a surgery to try and preserve binaural hearing if we can for as long as possible in these patients. So in conclusion, the ideal patient for an MFA, that's middle fossa approach, is an intracranial tumor with less than one centimeter intracisternal tumor extension. So Koos 1 or 2 tumor involving the lateral IAC and good hearing. And in general, for patients undergoing middle fossa for vestibular schwannoma, the hearing preservation rates were 37 to 82% and the outcomes have been improving generally in the most recent literature. But I do believe that this is the asymptote. This is probably the limit for this. I've been struggling with this problem for most of my career trying to preserve hearing in these patients and I've reached about an 80% asymptote in the last 50 patients. And I think that it's other factors that I showed you that are important and we should improve them and it'll be iteratively improved hopefully. So this is the techniques that I use. So obviously, we use ABR monitoring and everybody we're trying to preserve here. Wide opening of the IAC, as I mentioned. Decompress the tumor. This allows you then to remove the tumor atraumatically and you're not pulling out a like a football from the canal and compressing the nerves when you're pulling it up. So you need to decompress the tumor properly, even in a small tumor. Careful dissection, medial to lateral. You don't wanna pull the five rolls of the eighth nerve as it goes through into the cochlea. And so, you've gotta be very gentle about tractions. We'll go medial to lateral in most cases. Preoperative Nimodipine, we load them on preoperatively. There is literature on this. It's probably helpful in a number of patients. Blood pressure management, keep the MAPs elevated during surgery. I use papaverine dilute solution. I cut it one to nine and I use it routinely over the seventh and eighth nerves when I'm dissecting on them because I think a lot of the hearing loss is probably vascular and it's the labyrinthine artery in spasm. And so, we'll do everything we can to keep it perfused well. And postoperative hydration for three days. I do that routinely just for the same reason. I wanna keep the patient hydrated to keep the pipes full. So this study showed good hearing preservations of 78%, 80% in the last 50 patients. The middle fossa approach I think is a good viable alternative for ones that go far laterally. And obviously, the pre-operative hearing is the most important factor. This overlap between the fundus of the IAC and the cochlea are independently associated with poor hearing outcomes, most likely to limit any surgical exposure. And then, this high DWI signal in within the tumor and the tumor touching the modiolus are related to loss of hearing. And I don't know why this is true, whether this is inflammatory, it's not infarction. It's preoperative and they've got hearing preservation. So I don't know what it represents, but it may be inflammatory. And you can see the high DWI in the adjacent modiolus. And then, while this cohort represents the largest series of middle fossa approach for vestibular schwannoma, some patients lost to follow up. It's a single center. Obviously, we needs to be reproduced. And I'd like to see this reproduced in other centers. So I can't see the top of the slide, but I think you need... Yeah, go ahead.

- [Aaron] They'll be able to see it, Bill, so we'll be okay. Thank you.

- So I think we need to think about hearing preservation and restoration. Obviously, it needs to be higher on our priority list than it's been for the management of vestibular schwannomas because it's a huge quality of life factor for patients. And I think the problems that we have with the current technology is that with hearing aids and the BAHA, you can restore sound localization and, you can restore sound but you can't restore sound localization. Cochlear implants are probably the best option for you. And then, obviously, a brainstem implant if all else fails. And we'd like to try and preserve the cochlear nerve no matter what approach we're using. So if you're using a retrosigmoid approach and you can preserve the cochlear nerve, that's really helpful for considering a cochlear nerve implant either at the time of surgery or after surgery. And so, we need to try and do a better job at preserving that. If the patient has been deaf for years already, then we may consider just sacrificing the eighth nerve. But on the smaller tumors, we'd like to preserve the cochlear nerve and they can test it intraoperatively if they're doing a trans lab approach and then place a cochlear nerve implant. And then, obviously, there's a lot of literature on this, but I'd like to emphasize to the neurosurgeons involved in this tumor that this is a sort of the goal for the next generation here is hearing restoration. And there's a lot of wonderful work being done by our ENT colleagues on this. This is a paper by Neil Patel who's with us and showing that you can have functional hearing restoration after vestibular schwannoma resection. And you can do it after the resection of the tumor or simultaneous with a vestibular resection. Now we'd like to do it simultaneously if we do, if we can. If we can preserve the cochlear nerve, go ahead and try to place a cochlear implant. The problem that we're having is with the payers in that oftentimes, the payers won't authorize both procedures at the same operation. So, it's really a practical issue for us. And you can see that you can preserve hearing with these cochlear implants and see three pf five and maintain, achieved open speech. And these are important factors to consider and the search for optimal SRS parameters and surgical techniques for durable hearing preservation should be a goal. There's a growing interest in cochlear implant as a rehab option in vestibular schwannoma patients. Role of cochlear nerve function and integrity in decision making at the time of surgery is important. And finally, Luke, let's go to video. This is that giant schwannoma that I showed you at the beginning of the talk and I thought you might be interested. This has just been published and this shows how complicated some of these tumors can be. This is a 20 year old woman and she presented following a syncopal episode. She had a facial palsy diagnosed at age 10. So 10 years previously with incomplete function. So she never had a scan at that time and she had onset of hearing loss 10 years ago. And so, she's also has difficulty with her tongue now. And you can see this tumor, she's very thin and she's having difficulty eating at this point. And her extraocular movements were intact. She had V2 numbness. She had House-Brackmann 3 out of 6 and sensorineural hearing loss. And she had a 12th nerve palsy. So you can see the size of this tumor on the scan. Her general other neurological examination was fine, but she had vocal fold paresis, which we anticipated with her problems with swallowing. She had complete hearing loss.. The other side was fine. And this is her imaging and this just shows you how big the tumors can grow. And this is an interesting one because we used every approach to vestibular schwannoma to remove this tumor. And I didn't even know at the beginning of this case whether this truly was an acoustic tumor or not, but I think you'll see it likely was. It was extending throughout the petrous bone, occupying the petrous bone, and was extending through the jugular foramen. And I just want to emphasize that we can use these temporal bone approaches to remove tumor in the jugular foramen. And we're just writing a technical note on this right now. So we control the ventricles. She had some hydrocephalus, put an EVD in. Lateral position. And we'll use a combined petrosal approach. So we're gonna expose the middle fossa and the posterior fossa here and do a transmastoid approach. We use a translabyrinthine and transcochlear approach. So middle fossa, translabyrinthine, transcochlear, retrosigmoid, And debulk the tumor and we do abdominal fat harvest. So we did this in two stages. And the reason that we did this is I called this, because she was so small and thin and we had lost a fair amount of blood, the tumor was very vascular. So we did this over two stages with one week to resuscitate the patient between stages. So we'll start by the combined petrosal flap, lift off this L-shaped bone flap, and then, expose the middle fossa. And so, he's gonna oversaw the external artery auditory canal, remove the malleus here, and oversaw the canal. That way you don't need to worry about CSF leak through the canal. She's deaf already. Do a standard translab approach. Expose the sigmoid sinus and he's gonna make a fallopian bridge. And this is the fallopian bridge technique and this is where you leave the facial nerve in the canal and you expose labyrinthine segment as well. But you don't dissect the facial nerve directly. So after the temporal bone drilling is done, what I'm doing here is I'm gonna go ahead and debulk the tumor in the posterior fossa. And we'll go ahead and start the debulking again, wide opening. Drill and then take it down like an ashtray. And then, bring the capsule in and remove the capsule. There's the fifth nerve. Giant, very vascular tumor. Lower cranial nerves on the inferior aspect here. And this gives you beautiful exposure 'cause you can work around it and underneath the facial nerve and remove all the tumor. There's the petrous apex. So, we're looking right into the petrous apex from inside the temporal bone approach. We'll continue to be bulking from the retrosigmoid approach. Five again and you'll see six shortly. Remove the tumor from the jugular foramen in here. And then at this point, we had lost a fair amount of blood. We closed eustachian tube. And Rich Regergel, who's our otologist here, is packing the station tube with a piece of muscle so you don't get a CSF leak through the nose. Put fat graft around the fallopian bridge, close the dura, and then we'll go ahead and close the flap. And then, she's resuscitated for a week and we'll bring her back and remove the rest of the tumor. After stage one, you can see what we've achieved. We've got tumor left in the jugular foramen. We've got tumor left in the petrous apex and also tumor in the posterior fossa. So, we'll bring her back again retrosigmoid and continue with the dissection. And there's the upper part of the tumor, sixth nerve, and we monitor for these cranial. Fourth nerve above us. And then, there's six entering Dorello's canal. You wanna really be careful of sixth nerve on these larger acoustics because it can get involved with the dissection. Anterior petrosal approach, middle fossa. And again, removing more tumor from the middle ear. And now, we're reaching down into the region of the jugular foramen. We're going extracranial through the jugular foramen and through this transtemporal approach, all the way down into the upper neck and the carotid arteries there. And we expose the carotid artery in the vertical segment within the temporal bone. There's the seventh nerve. Now, we'll dissect the tumor off the facial nerve, preserve, which was well preserved in this case despite the fact that she had a House-Brackmann 3 out of 6. The nerve was quite robust, so we're stimulating the root exit zone of the seventh nerve. Petrous Apex is completely cleaned of tumor and we'll remove the loss of tumor inferiorly from the jugular foramen. Going out in the neck, approach the transotic approach, sigmoid sinus, and the retrosigmoid, and middle fossa, which was done through here. Stimulating the seventh nerve at the brain stem, which is right here. And in the sixth nerve rendering drills canal. The basilar artery. The middle ear. And here's foramen spinosum right there. So we'll close at this point We'll wax all the air cells that we see. Again, he'll put another piece of muscle down the eustachian tube. Close the dural with the dural substitute. This is AlloDerm in this particular case that we'll use, which is great for closing posterior . And then, close in the usual way. And you can see the scan. This is the immediate postop scan. We just saw periphery enhancement. We just thought this was post-surgical. And then I think we've got a delayed scan which shows complete removal after several months. We were able wean the EVD after a week or so. She underwent a vocal cord injection. Yeah, day eight the ventriculostomy was removed and she was ambulating and doing well. And she was discharged with outpatient speech therapy on post-op day 15. And I think we have a delayed scan on her. Yes, four month follow up scan. You can see the ventricles are now normal size and she's had a good outcome. And her facial nerve palsy return may be a little bit better than it was before, but no worse. She had obviously absent hearing and she was otherwise neurologically intact. So thanks Luke. I think that's it. Let's go back to slides. And I think that's the end of the talk. Aaron, I'm happy to answer any questions for you.

- Very informative, really enjoyed watching it, Bill. Just a few points, emphasizing that loss of hearing in one ear is really a challenge to live with. I think as neurosurgeons, we sort of consider loss of hearing unilateral, not a big deal and that's just sort of part of the process. But in fact, the patient is unable to differentiate or distinguish where the voice is coming from. So, they will lose that sense of orientation or audio orientation. In other words, is this person on the right or left side talking to them, is the car coming from left or from right. And that can be at times very, very challenging in the quality of life as you mentioned. So I wanna just remember, remind everyone that that is a big deal. And I know and neurosurgeons, historically, have not addressed that very much. Number two is really the issue of for the middle fossa approach to decompressing the bone or drilling in more than 180 degrees. You really have to get almost 260 or 70 degrees to avoid any insult on the nerve, on the cochlear nerve under you. Because if you are not, the unroofing and plus more during manipulation, you're gonna injure the nerve because it's so extremely sensitive to any traction or any compression. So emphasizing that really extra more than 180 degree decompression is a paramount. And then that, you know, magic hook technique you showed that you just sort of dig in your hook and lift it up rather than pushing down and traction and pulling and you have to be very aware of that. That these very fine technical nuances are critical on an nerve that is extremely sensitive, right, the cochlear nerve. And importantly, papaverine. These, you know, vasospasm again underrated in neurosurgery. We do that for every surgery essentially. That the perforators or the vessels are manipulated. We irrigate the entire field with papaverine and leave it there before we close the dura. So every case I do, we have diluted papaverine after hemostasis occur. When we're closing the dura, the last few stitches, we just inject papaverine just to relax everything in there. And I think these surgeries, like middle fossa, where the nerve vascular feeders that are very tiny on its walls could be affected probably. What I try to use is a piece of gelfoam soaked and thrombin.

- Right.

- And I just massage it. Because if you irrigate, it just runs out of the field. So having an ability to put that gelfoam on the nerve if you're not working with it and let it soak in the papaverine is a critical component in my opinion. What are your thoughts there, Bill?

- Yeah, I think yeah, you've mentioned, and you've emphasized obviously the important features. One of the things, when you need to use your non-dominant hand with the suction, and I can't emphasize this enough, and this is where experience comes in and I teach my fellows this, is that you're using, I use a Fujita sucker so I can just use the thumb control and variable the throttle on it. And I use it to hold the tumor up. So when I'm making the cut with the scissors, I use it to stabilize the tumor. So I'm not pushing the tumor every time and moving the tumor every time I'm touching it. And so, I stabilize the tumor with my suction hand using variable amounts of suction. Stabilize it, cut the pieces of tumor out, and then we just gently lift it off with a wonder hook. And so it takes a while to sort of get all these things to work together, but that's what the young people need to think about is that when I train residents and fellows, I always see them coming in early that they don't know how to use their non-dominant hand as an equal player in the dissection. And you've gotta learn those techniques with holding the suction and modulating the suction. And so people, you come from different places where they use different suctions and that kind of thing, but that's how I do it. And I think that's a critically important thing is to, you don't wanna move that tumor around because you're gonna just pull those fibrils right outta the modiolus of the eighth nerve. So you've really gotta stabilize everything while you're dissecting.

- Yeah, very well said. You know, I'm completely a believer of the mouth switch. And I do believe using the mouth switch gives you a third hand. And when you have the mouth switch, you can really focus, you can, because you can work under higher magnification. Because at such high magnification, any special movement can get the image out of focus. And after a while, you get frustrated because you have to take out your hand again. You have to adjust the focus and then bring the, get the instruments. You almost compromise on delicacy of the surgery even subconsciously. So you have to make the microscope a piece of your face, like a pair of glasses, and then you can work on very high magnification because then that gives you an ability to visualize better That's-

- Right.

- Number one. And number two is you gotta be an ambidextrous surgeon. It is fine microsurgical movement require really an ability to use your non-dominant hand, in my case, my right hand because I'm left-handed, very, very effectively. Because if you don't, then you have to use traction, pushing, shoving to make up for that extra hand that is not helping you to stabilize the tumor mass. There's just no way around it and these are subconscious. You know, people say "I don't do it," but then when I watch their videos, they're doing it routinely. but they're not aware of it because subconsciously, you don't have any other solution. Therefore, you have accepted it as part of the operation.

- Yeah, I think it just becomes, you end up defaulting training yourself to do that because you realize. The other thing I would say about this microscope, so you obviously these middle fossa dissections are done under the highest magnification of the scope. It's like doing a bypass, right? And the one advantage, there's nothing good about getting older, but when the advantage of the older surgeon is that, and I'm sure you notice this Aaron, that when you, when I scrub in with the residents and the fellows is the microscope is never in the right field depth of you, right? And they don't notice it because their lenses are much more mobile and they can adjust for it. But the older surgeon keeps it in the plane of the field of view and keeps it beautifully there. So, the videos of an older surgeon are usually clearer and more crisp because they're always in focus. And so, but it's also good for that tumor 'cause then, you know, if you're out of focus, you're pulling the tumor up or down and people don't appreciate that as much.

- Right. I cannot, you know, Bill, emphasize this fact and I've done that for decades, as I'm sure you have, that it's not about just jumping and trying to do the case. There's so many other preparation and nuances as a neurosurgeon of how to use a microscope, how to use both of your hands and get to that flow. There's a flow really you have to reach where you feel like you are a part of the microscope. There's nothing between you and the tumor. The microscope is just a piece of you and your hands are extremely well-orchestrated, like a beautiful symphony. And just everything is really flowing in that's smooth sort of ballet rather than a break dance. It's just such a critical importance of surgery more than anything else. More than I'm doing a big tumor, I'm doing part of the case, I'm proud of myself. I think we should all step back and say, "Let's look at the basics." Are we able to manage the microscope? Are we gonna use both of our hands? Are we gonna be able to really use the techniques on high magnification to protect vital structures?"

- Right.

- Something I think has been lost in the art of microsurgery in my opinion.

- Yeah. Also I think, you know, I don't think we should cheapen any of this stuff because it takes you a lot of experience and years to learn all these little technical nuances. And I emphasize to the residents and the fellows that when you finish your training, you are just beginning to be a surgeon. You're in your infancy and it's going to take the next decade or two before you become really confident and you reach the top of your game. And that's just the nature of the beast. This is highly technical, it's highly nuanced. You need a lot of haptic feedback to learn. And you're not going to do it and you're not an expert when you finish your fellowship. And I can't emphasize that enough because I see the young people always in a rush. And I just think that, you know, they have to learn from the senior people, be as safe as they can, go slow, be safe, keep the patient safe, and then learn your experience safely over the next, you know, decade or two. And I think it's also helpful to have a senior person around to help 'cause some of these cases are impossibly complicated. And it's always good to have a senior person around to offer the best care for the patient.

- I agree. I agree. Lemme tell you, I look at my own videos, my own videos have been probably one of my greatest teachers reviewing it with senior people. And when I look at my videos 10 years ago, I really sort of sit down and have this sinking feeling that is was that really what I did? Is that what I did? And it really makes you feel like how much a decade makes a difference in your career. And I say that about myself because it's easy for me, you know, be on the passenger seat and tell people how they have to do this or that and you know, why did this happen. But if you look at yourself and be more objective, you'll see that a decade of focusing on honing your, you know, improving your techniques makes a big difference in your own surgical videos. Nobody is as good as yourself in being your critic, a constructive critic. And I think that's of great value. So with that Bill, I wanna thank you again for an incredible mentorship you have had for me and for many young neurosurgeons. It's been truly an honor working with you. Thank you.

- Thank you, Aaron. Always great to work with you and so pleased to see the Atlas doing so well. Thank you.

- Thank you. Thanks very much.

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